The present invention relates to a method of handling mail items in a sorting machine having sorting outlets with sorting outlet bins into which the mail items are directed during successive sorting passes;
which method consists, during a first sorting pass for sorting the mail items, in taking a digital picture of each mail item bearing address information for the purpose of automatically recognizing the address of the mail item, in particular by Optical Character Recognition (OCR), in deriving from said picture a digital fingerprint which is a logic identifier for the mail item, and in recording in a memory address data representing the automatically-recognized address of the mail item in correspondence with the digital fingerprint of the mail item and with a logic identifier of the sorting outlet bin into which the mail item is directed; and
during a second sorting pass for sorting the mail items, in taking, once again, a digital picture of a current mail item bearing address information for the current mail item, in deriving from said picture a digital fingerprint for the current mail item, and in searching among the digital fingerprints recorded during the first sorting pass for a match with the digital fingerprint of the current mail item, in order to retrieve, in particular the address data representing the address information of the current mail item.
More particularly, the invention relates to a method of automatically sorting mail items in a plurality of passes through one or more sorting machines in which it is not necessary to affix (by printing, optionally on a label) a mail item identifier or “ID tag” to the mail items, in particular an ID tag in the form of a barcode. In the method of the invention, the mail items are identified by a digital “fingerprint” or image signature as described in European Patent Document EP 1 222 037. The use of digital fingerprints or image signatures for identifying the mail items during the successive sorting passes makes it possible to avoid using printer and barcode reader peripherals, to avoid using verifier peripherals for verifying the quality of printing of the barcodes (such verifier peripherals being commonly referred to as “BCVs” (barcode verifiers) in the literature), and to avoid using labelers for sticking labels onto those of the mail items which have plastics surfaces (in particular “flats”, i.e. flat mail items such as magazines and newspapers), with this resulting in substantial savings in the cost of the sorting machine and in the cost of maintenance thereof, and also in consumables while the machine is in use.
In Patent Document EP 1 222 037, a barcode is affixed to a wall of each sorting outlet bin, that barcode serving as an identifier for the bin. During the second sorting pass, the barcodes of the bins loaded into the inlet of the machine are read, and an association is made between those bins and the digital fingerprints of the mail items contained in said bins, so that, when a search is conducted in the second pass for a match between the digital fingerprint of a current mail item and the digital fingerprints recorded in the first pass, an exploration space is used that is limited to the fingerprints of the mail items of a single first-pass sorting outlet bin so as to satisfy the requirements of real-time handling. But in that known method, the principle used for reducing the exploration space for exploring digital fingerprints cannot accommodate mail items contained in a plurality of sorting outlet bins from a first sorting pass through a machine be transferred into a single bin so as to be recycled to the inlet of another machine for continuing with the second sorting pass. With that known method, it is also not possible to have breaks in the sequence of the bins, e.g. it is not possible to insert into the second sorting pass mail items contained in a bin that is not a sorting outlet bin coming from the first sorting pass. With that known method, it is essential, in the second pass, to preserve the relative order of the mail items in each bin recycled to the inlet of the sorting machine. That known method thus cannot withstand disturbances that might occur in the feed storage space of the sorting machine, e.g. as a result of the machine jamming.
An object of the invention is to provide a method of sorting mail items in a plurality of sorting passes that uses digital fingerprints to identify the mail items and that is not sensitive to the above-indicated operating constraints.